Sensors for measuring at least one of pressure and temperature, sensor arrays and related methods

ABSTRACT

Arrays of resonator sensors include an active wafer array comprising a plurality of active wafers, a first end cap array coupled to a first side of the active wafer array, and a second end cap array coupled to a second side of the active wafer array. Thickness shear mode resonator sensors may include an active wafer coupled to a first end cap and a second end cap. Methods of forming a plurality of resonator sensors include forming a plurality of active wafer locations and separating the active wafer locations to form a plurality of discrete resonator sensors. Thickness shear mode resonator sensors may be produced by such methods.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional PatentApplication Ser. No. 61/432,433, filed Jan. 13, 2011 entitled “Sensorsfor Measuring At Least One of Pressure and Temperature, Sensor Arraysand Related Methods,” the disclosure of which is incorporated herein byreference in its entirety.

TECHNICAL FIELD

Embodiments of the present disclosure relate to sensors for measurementof at least one of a pressure and temperature and, more particularly, toquartz resonator sensors for measurement of at least one of a pressureand temperature and related methods thereof.

BACKGROUND

Thickness shear mode quartz resonator sensors (also interchangeablycalled quartz resonator transducers) have been used successfully in thedown-hole environment of oil and gas wells for several decades and arestill an accurate means of determining bottom-hole pressure andtemperature. Quartz resonator pressure and temperature sensors typicallyhave a crystal resonator located inside a housing exposed to ambientbottom-hole fluid pressure and temperature. Electrodes on the resonatorelement coupled to a high frequency power source drive the resonator andresult in shear deformation of the crystal resonator. The electrodesalso detect the resonator response to at least one of pressure andtemperature and are electrically coupled to conductors extending toassociated power and processing electronics isolated from the ambientenvironment. Ambient pressure and temperature are transmitted to theresonator, via a substantially incompressible fluid within the housing,and changes in the resonator frequency response are sensed and used todetermine the pressure and/or temperature and interpret changes in same.For example, a quartz resonator sensor, as disclosed in U.S. Pat. Nos.3,561,832 and 3,617,780, includes a cylindrical design with theresonator formed in a unitary fashion in a single piece of quartz. Endcaps of quartz are attached to close the structure.

Generally, a thickness shear mode quartz resonator sensor assembly mayinclude a first sensor in the form of a primarily pressure sensitivequartz crystal resonator exposed to ambient pressure and temperature, asecond sensor in the form of a temperature sensitive quartz crystalresonator exposed only to ambient temperature, a third reference crystalin the form of quartz crystal resonator exposed only to ambienttemperature, and supporting electronics. The first sensor changesfrequency in response to changes in applied external pressure andtemperature with a major response component being related to pressurechanges, while the output frequency of the second sensor is used totemperature compensate temperature-induced frequency excursions in thefirst sensor. The reference crystal, if used, generates a referencesignal, which is only slightly temperature-dependent, against orrelative to which the pressure- and temperature-induced frequencychanges in the first sensor and the temperature-induced frequencychanges in the second sensor can be compared. Means for such comparisonas known in the art include frequency mixing or using the referencefrequency to count the signals for the first and second sensors.

Prior art devices of the type referenced above including one or morethickness shear mode quartz resonator sensors exhibit a high amount ofaccuracy even when implemented in an environment such as a down-holeenvironment exhibiting high pressures and temperatures. However, suchthickness shear mode quartz resonator sensors may be relativelyexpensive to fabricate, as each sensor must be individuallymanufactured. These relatively expensive quartz resonator sensors maynot be economically practical for implementation in applications thatwould benefit from their relatively higher accuracy and ability tooperate in a relatively wider range of temperatures and pressures ascompared to other less expensive, less accurate and less robust sensorssuch as strain or piezoresistive gages.

BRIEF SUMMARY

In some embodiments, the present disclosure includes an array ofresonator sensors including an active wafer array comprising a pluralityof unsingulated active wafers, a first unsingulated end cap arraycoupled to a first side of the active wafer array, and a secondunsingulated end cap array coupled to a second side of the active waferarray. Each unsingulated active wafer comprises a resonating portionwherein the resonating portion of each unsingulated active wafer is outof contact with each of the first and second unsingulated end caparrays.

In some embodiments, the present disclosure includes a plurality ofthickness shear resonator sensors produced by a process includingforming a plurality of active wafer locations in a first sheet ofmaterial comprising locating a central portion of each active wafer ofthe plurality of active wafer locations, bounding the plurality ofactive wafer locations about the central portions thereof to form afirst cavity on a first side of each central portion and a second cavityon a second side of each central portion to form an array of resonatorsensors, and separating the array of resonator sensors.

In yet additional embodiments, the present disclosure includes a methodof forming a plurality of resonator sensors. The method includes forminga plurality of active wafer locations in a unitary structure, coupling aplurality of first end cap structures to a first side of the unitarystructure, coupling a plurality of second end cap structures to asecond, opposing side of the unitary structure, and separating theplurality of active wafer locations laterally between the end capstructures to form a plurality of discrete resonator sensors.

In yet additional embodiments, the present disclosure includes a methodof forming a plurality of resonator sensors. The method includes forminga plurality of active wafer locations in a first sheet of materialcomprising locating a central portion of each active wafer of theplurality of active wafer locations, bounding the plurality of activewafer locations about the central portions thereof to form a firstcavity on a first side of each central portion and a second cavity on asecond side of each central portion to form an array of resonatorsensors, and separating the array of resonator sensors to form aplurality of discrete resonator sensors.

In yet additional embodiments, the present disclosure includes athickness shear mode resonator sensor. The thickness shear moderesonator sensor includes an active wafer comprising a resonatingelement and a first end cap coupled to a first side of the active waferwhere at least one surface of the active wafer and at least one surfaceof the first end cap form a first cavity between the resonating elementof the active wafer and the first end cap. The thickness shear moderesonator sensor also includes a second end cap coupled to a second,opposing side of the active wafer where at least one surface of theactive wafer and at least one surface of the second end cap form asecond cavity between the resonating element of the active wafer and thesecond end cap. The active wafer exhibits a substantially quadrilateralcross section taken in a direction along an interface of the activewafer and at least one of the first end cap and the second end cap.

BRIEF DESCRIPTION OF THE DRAWINGS

While the specification concludes with claims particularly pointing outand distinctly claiming what are regarded as embodiments of the presentdisclosure, various features and advantages of embodiments of thedisclosure may be more readily ascertained from the followingdescription of example embodiments of the disclosure provided withreference to the accompanying drawings, in which:

FIG. 1 is a perspective view of resonator sensor in accordance with anembodiment of the present disclosure;

FIG. 2 is a perspective cutaway view of an active wafer of the resonatorsensor shown in FIG. 1;

FIG. 3 is a cross-sectional side view of the resonator sensor shown inFIG. 1;

FIG. 4 is a cross-sectional side view of a resonator sensor inaccordance with another embodiment of the present disclosure;

FIG. 5 is a cross-sectional side view of a resonator sensor inaccordance with yet another embodiment of the present disclosure;

FIG. 6 is a cross-sectional side view of a resonator sensor inaccordance with yet another embodiment of the present disclosure;

FIG. 7 is a top view of an active wafer of a resonator sensor inaccordance with yet another embodiment of the present disclosure;

FIG. 8 is a top view of an array of active wafers for use in resonatorsensors in accordance with yet another embodiment of the presentdisclosure;

FIG. 9 is a top view of a portion of the array of active wafers shown inFIG. 8;

FIG. 10 is a cross-sectional side view of an array of resonator sensorsin accordance with yet another embodiment of the present disclosure; and

FIG. 11 is a cross-sectional side view of the array of resonator sensorsshown in FIG. 10 that have been separated to form individual resonatorsensors.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying drawings that depict, by way of illustration, specificembodiments in which the disclosure may be practiced. However, otherembodiments may be utilized, and structural, logical, andconfigurational changes may be made without departing from the scope ofthe disclosure. The illustrations presented herein are not meant to beactual views of any particular sensor or component thereof, but aremerely idealized representations that are employed to describeembodiments of the present disclosure. The drawings presented herein arenot necessarily drawn to scale. Additionally, elements common betweendrawings may retain the same numerical designation.

It is noted that in some of the drawings presented herein, embodimentsof resonator sensors and components thereof are shown as being at leastpartially transparent in order to facilitate description of embodimentsof the present disclosure. However, it is understood that materials(e.g., quartz) used to form the resonator sensors and components thereofmay be transparent, opaque, variations therebetween, or combinationsthereof

FIG. 1 is a perspective view of a resonator sensor according to thepresent disclosure. As shown in FIG. 1, the resonator sensor such as,for example, a quartz resonator sensor 100 includes an active wafer 102at least partially disposed in a housing 104. A portion of the activewafer 102 may be bounded on sides thereof. For example, the housing 102may include two end caps (e.g., a first end cap 106 end and a second endcap 108) and the active wafer 102 may disposed between the end caps 106,108 forming the housing 104. An actively vibrating portion of the activewafer 102 (e.g., a resonating portion 114 (FIG. 2)) includes a cavity onboth sides enabling the portion of the active wafer 102 to resonate(e.g., displace, vibrate, etc.) when electrically driven at one or moreselected frequencies. For example, the active wafer 102 may include arecessed portion 110 forming a central portion of the active wafer 102(e.g., a resonating portion 114 (FIG. 2)) having a thickness that isless than a thickness of an adjacent portion of the active wafer 102(e.g., the outer portion 116 (FIG. 2)). In some embodiments, activewafer 102 may include a recessed portion 110 on opposing sides of theactive wafer 102 (e.g., opposing faces of the active wafer 102).

In some embodiments, the resonator sensor 100 may have a substantiallycuboidal shape. For example, the resonator sensor 100 may exhibit afirst substantially quadrilateral (e.g., square) cross-sectional shapeand a second substantially quadrilateral cross-sectional shape in adirection substantially transverse to the first cross section. It isnoted that, while the embodiment of FIG. 1 illustrates a resonatorsensor 100 having a substantially quadrilateral cross-sectional shape,in other embodiments, a resonator sensor may be formed in othergeometries (e.g., a circular or disc cross-sectional shape, a polygonalcross-sectional shape, etc.). For example, a resonator sensor may beformed in a substantially cylindrical shape (e.g., the resonator sensormay be somewhat similar to those shown in the above-referenced U.S. Pat.Nos. 3,561,832 and 3,617,780). In an embodiment, resonator sensors 100initially formed with a substantially quadrilateral cross-section asdescribed herein may subsequently be formed, for example by grinding ona lathe, into a substantially cylindrical shape. As used herein, theterm “substantially cylindrical” does not exclude one or more flats onthe exterior of the resonator, and specifically includes shapes havingan arcuate outer surface comprising one or more radii, such asellipsoidal shapes.

FIG. 2 is an enlarged, perspective cutaway view of the active wafer 102.As shown in FIG. 2, the active wafer 102 may include a first recessedportion 110 formed in a first face of the active wafer 102 and a secondrecessed portion 111 in a second, opposing face of the active wafer 102.The one or more recessed portions 110, 111 may form a resonating portion114, which may also be characterized as a resonator element, of theactive wafer 102. In other words, the active wafer 102 may comprise aninverted mesa structure having the resonating portion 114 formed by thefirst and second recessed portions 110, 111 in the center region of theactive wafer 102 and a thicker outer portion 116 surrounding theresonating portion 114. In some embodiments, the first recessed portion110 may be substantially aligned with the second recessed portion 111.For example and as shown in FIG. 2, the recessed portions 110, 111 aresubstantially aligned with each other (e.g., each point on the outerboundary of the recessed portion 110 is substantially collinear to asimilar point of the recessed portion 111).

In some embodiments, portions of the active wafer 102 may be removed toform the recessed portions 110, 111. For example, portions of the activewafer 102 may be removed using an etching process, an abrasiveplanarization process such as, for example, a chemical-mechanicalpolishing (CMP) process, or a combination thereof. Etching processes mayinclude, for example, removing portions of the material using a mask(e.g., through photolithography patterning or the like) and a reactiveion (i.e., plasma) etching process or removing the material using a maskand an isotropic wet chemical etching process. It is noted that theparticular composition of the gases used to generate the reactive ions,the particular composition of the chemical etchant, and the operatingparameters of the etching process may be selected based on thecomposition of the mask, the material to be etched, and the surroundingmaterials.

It is noted that the removal techniques discussed above may be utilizedto form recesses in other portions of the resonator sensor, for example,one or more of the end cap as discussed below.

The active wafer 102 may include one or more electrodes formed thereon.For example, electrodes 112, 113 may be provided on the opposingrecessed portions 110, 111 forming the resonating portion 114 of theactive wafer 102. The electrodes 112, 113 may be formed on the activewafer by, for example, deposition techniques (e.g., chemical vapordeposition (CVD), physical vapor deposition (PVD), atomic layerdeposition (ALD), sputtering, thermal evaporation, or plating). In someembodiments, the electrodes 112, 113 may be formed from gold with anintermediate layer of chromium between the gold and the quartz activewafer 102 to enhance adhesion. As known in the art, the electrodes 112,113 are provided to excite vibrational behavior in the resonatingportion 114 of the active wafer 102, and are electrically coupled byconductors (not shown in FIG. 2) to a high-frequency drivingelectronics, as is conventional.

Referring still to FIG. 2, the resonating portion 114 may be a flatresonator (i.e., plano-plano). In other embodiments, a resonatingportion 114 or a portion thereof may comprise other shapes such as, forexample, plano-convex, etc. In plano-convex resonators, the outerportion 116 surrounding the resonating portion 114 of the active wafer102 on each side of the active wafer 102 may be substantially flat toenable coupling to the end caps 106, 108.

FIG. 3 is a cross-sectional side view of the resonator sensor 100. Asshown in FIG. 3, the end caps 106, 108 may be coupled to the activewafer 102 by, for example, an adhesive or bonding process (e.g., a fusedglass frit 118). The recessed portions 110, 111 of the active wafer 102and the end caps 106, 108 form cavities 120, 121 on opposing sides ofthe resonating portion 114 that enable the resonating portion 114 tovibrate freely. The electrodes 112, 113 may include a portion (e.g.,conductive traces 122, 123) extending along the active wafer 102 (e.g.,along the resonating portion 114 and the outer portion 116) to an outerportion of the resonator sensor 100 to enable electrical connectionbetween the electrodes 112, 113 and, for example, an electronicsassembly. In some embodiments, the fused glass frit 118 formed betweenone or more end caps 106, 108 and the active wafer 102 proximate to theconductive traces 122, 123 may not extend to an outer surface of theresonator sensor 100. Stated in another way, a recess 124 may be formedin the glass frit 118 proximate the outer portion of a joint formedbetween one or more end caps 106, 108 and the active wafer 102 such thatthe conductive traces 122, 123 may be partially exposed at an outerportion of the resonator sensor 100 to enable electrical connectionthereto.

FIG. 4 is a cross-sectional side view of a resonator sensor 200 inaccordance with another embodiment of the present disclosure. It isnoted that the cross-sectional side view of a resonator sensor 200 istaken in direction transverse to the cross-sectional side view of theresonator sensor 100 shown in FIG. 3. As shown in FIG. 4, the resonatorsensor 200 may be somewhat similar to the resonator sensor 100 and mayinclude similar elements and methods of forming as shown and describedabove with reference to FIGS. 1 through 3. For example, the resonatorsensor 200 may include an active wafer 202, housing 204, end caps 206,208, and electrodes 212, 213. The active wafer 202 of the resonatorsensor 200 may include a first recessed portion 210 formed in a face ofthe active wafer 202 such that the active wafer 202 includes aresonating portion 214 and a relatively thicker outer portion 216. Asecond recessed portion 211 may be formed in a face of the one of theend caps (e.g., end cap 206). The recessed portions 210, 211 may formcavities 220, 221 on opposing sides of the resonating portion 214 of theactive wafer 202 to enable the resonating portion 214 to vibrate orotherwise displace under a force applied thereto. One or more of theelectrodes 212, 213 may include a conductive trace 222 extending alongthe active wafer 202 (e.g., along the resonating portion 214 and theouter portion 216).

FIG. 5 is a cross-sectional side view of a resonator sensor 300 inaccordance with another embodiment of the present disclosure. Similar toFIG. 4, the cross-sectional side view of a resonator sensor 300 is takenin direction transverse to the cross-sectional side view of theresonator sensor 100 shown in FIG. 3. As shown in FIG. 5, the resonatorsensor 300 may be somewhat similar to the resonator sensors 100 and 200and may include similar elements and methods of forming as shown anddescribed above with reference to FIGS. 1 through 4. For example, theresonator sensor 300 may include an active wafer 302, housing 304, endcaps 306, 308, and electrodes 312, 313. A first recessed portion 310 maybe formed in a face of the one of the end caps 306. A second recessedportion 311 may be formed in a face of an opposing end cap 308. Theactive wafer 302 of the resonator sensor 300 may include a resonatingportion 314 and an outer portion 316 having substantially the samethickness. The recessed portions 310, 311 formed in the end caps 306,308 may form cavities 320, 321 on opposing sides of the resonatingportion 314 of the active wafer 302 to enable the resonating portion 314to vibrate or otherwise displace under a force applied thereto. One ormore (e.g., both) of the electrodes 312, 313 may include conductivetraces 322 extending along the active wafer 302 (e.g., along theresonating portion 314 and the outer portion 316).

FIG. 6 is a cross-sectional side view of a resonator sensor 350 inaccordance with yet another embodiment of the present disclosure. Thecross-sectional side view of a resonator sensor 350 is taken indirection similar to that of the cross-sectional side view of theresonator sensor 100 shown in FIG. 3. As shown in FIG. 6, the resonatorsensor 350 may be somewhat similar to the resonator sensors 100, 200,and 300 and may include similar elements and methods of forming as shownand described above with reference to FIGS. 1 through 5. For example,the resonator sensor 350 may include an active wafer 352, housing 354,end caps 356, 358, and electrodes 362, 363. First recessed portions 360may be formed in a face of both of the end caps 356. Second recessedportions 361 may be formed in two, opposing faces of the active wafer352 such that the active wafer 352 includes a resonating portion 364 anda relatively thicker outer portion 366. The recessed portions 360 formedin the end caps 356, 358 and the recessed portions 361 formed in activewafer 352 may form cavities 370, 371 on opposing sides of the resonatingportion 364 of the active wafer 352 to enable the resonating portion 364to vibrate or otherwise displace under a force applied thereto. One ormore (e.g., both) of the electrodes 362, 363 may include conductivetraces 372 extending along the active wafer 352 (e.g., along theresonating portion 364 and the outer portion 366).

In some embodiments, the components of resonator sensors 100, 200, 300,and 350 may be fabricated from single crystal quartz, for example, fromquartz plates cut to exhibit an AT-cut, BT-cut, or other suitableorientation. In some embodiments, the resonator sensors 100, 200, 300,and 350 may include methods of fabrication, orientations, electronicassemblies, housings, reference sensors, and components similar to thesensors and transducers disclosed in, for example, U.S. Pat. No.5,471,882 to Wiggins, U.S. Pat. No. 4,550,610 to EerNisse et al., andU.S. Pat. No. 3,561,832 to Karrer et al., the disclosure of each ofwhich is hereby incorporated herein in its entirety by this reference.For example, dimensional characteristics of components of resonatorsensors 100, 200, 300, and 350 (e.g., dimensions of the end caps, activewafer, cavities, recesses, etc.) may be varied to adjust the pressureand/or temperature sensitivity thereof, by adjusting the stressexperienced by the center portion of resonating portion responsive toapplication of external pressure to the resonator sensors. In someembodiments, the resonator sensors 100, 200, 300, or 350 may beimplemented in a transducer including drive and signal processingelectronics similar to those described in, for example, U.S. Pat. No.5,231,880 to Ward et al., the disclosure of which is hereby incorporatedherein in its entirety by this reference, or any other suitablearrangement.

FIG. 7 is a top view of an active wafer such as, for example, activewafer 102. As shown in FIG. 7, the active wafer 102 may include arecessed portion 110 formed therein, a resonating portion 114, an outerportion 116, and electrode 112 formed on the resonating portion 114. Theelectrode 112 may include a conductive trace 122 extending from theresonating portion 114 to an edge of the active wafer 102. In someembodiments, a tab 126 may be formed proximate an edge of the activewafer 102 (e.g., formed along an edge of the active wafer 102). The tab126 may be electrically connected to the electrode 112 via theconductive trace 122 to enable an electronics assembly to be connectedto the electrode 112 via the tab 126 proximate the edge of the activewafer 102. In some embodiments, the tab 126 may be disposed on theactive wafer 102 (e.g., over or under the conductive trace 122) by, forexample, the deposition techniques described above. In some embodiments,a tab 126 may be formed from gold with an intermediate layer of chromiumbetween the gold and the quartz active wafer 102 to enhance adhesion. Insome embodiments, a portion of the tab 126 may overlap the recessedportion 110 of the active wafer 102. It is noted that while theembodiment of FIG. 7 illustrates one side (e.g., a first side) of theactive wafer 102, another side may be substantially similar to the sideshown in FIG. 7. For example, a second, opposing side of the activewafer 102 may be similar to the first side shown in FIG. 7; however, thesecond side may be a substantially mirror image of the first side (e.g.,as shown in FIG. 3).

In some embodiments, the active wafer 102 may be substantially square,having a length of approximately 0.240 inch (approximately 6.096millimeters) on each side. The active wafer 102 may have a thickness ofapproximately 0.004 inch (approximately 0.1016 millimeter).

In some embodiments, the resonating portion 114 (i.e., the recessedportion 110) and the electrode 112 may be formed to have a substantiallycircular shape. For example, the resonating portion 114 may have adiameter of between approximately 0.110 inch and 0.150 inch(approximately between 2.794 millimeters and 3.81 millimeters) and theelectrode 112 may have a diameter of between approximately 0.050 inchand 0.090 inch (approximately between 1.27 millimeters and 2.286millimeters).

In some embodiments and as discussed above with reference to FIG. 3, arecess 124 may be formed in the adhesive or bonding layer (e.g., theglass frit 118) adjacent a periphery of the sensor assembly. The recess124 may expose a portion of the tab 126 for forming electricalconnection between the electrode 112 and an electronics assembly via thetab 126.

FIG. 8 is a top view of an array of unsingulated active wafers for usein resonator sensors in accordance with yet another embodiment of thepresent disclosure. As shown in FIG. 8, an array 400 including aplurality of active wafers 402 may be formed as a unitary structure(e.g., a plate or sheet of cultured quartz having a thickness of, forexample, approximately 0.004 inch (approximately 0.1016 millimeter)). Insome embodiments, the plurality of active wafers 402 of the array 400may include the elements, features, and methods of forming of the activewafers 102, 202, 302 described above with reference to FIGS. 1 through7. For example, as shown in FIG. 9, the plurality of active wafers 402of the array 400 may include recessed portions 410 formed therein,resonating portions 414, outer portions 416, electrodes 412, and tabs426. In some embodiments, as represented by a portion of array 400 shownin dashed lines, a recess 424 may be formed (e.g., in the adhesionlayer, in the array, in the end caps, etc.) to expose portions of thetabs 426 for electrical connection thereto. For example, during adhesionor bonding of the array 400 to one or more ends caps (e.g., end caps106, 108 (FIG. 1)), the recess 424 may be formed at a corner portion oftwo or more active wafers 402 such that one recess 424 of the array 400may provide two to four individual recesses in the separate activewafers 402.

FIG. 10 is a cross-sectional side view of an array of resonator sensorsin accordance with yet another embodiment of the present disclosure. Asshown in FIG. 10, an array 500 including a plurality of quartz resonatorsensors 501 may be formed as a unitary structure. For example, the array500 including the plurality of quartz resonator sensors 501 may beformed from an array of active wafers 502 (e.g., array 400 of activewafers 402 as shown and described with reference to FIGS. 8 and 9). Thearray 500 including the plurality of quartz resonator sensors 501 mayinclude one or more arrays of end caps 506, 508, each array being formedas a unitary structure (e.g., one or more plates of cultured quartz athickness of, for example, approximately 0.070 inch (approximately 1.778millimeters)). In some embodiments, the ratio of the thickness of atleast one of the end caps 506, 508 to the thickness of the active wafers502 may be 10:1 or greater (e.g., 15:1, 17.5:1, 20:1, etc.).

As shown in FIG. 10, the array 500 including the plurality of quartzresonator sensors 501 may be separated (e.g., singulated) to formindividual resonator sensors 501 (FIG. 11). For example, the array 500including the plurality of quartz resonator sensors 501 may be separatedalong dashed lines 503 (e.g., separated along a plane transverse tointerfaces between the array 400 of active wafers 402 and the arrays ofend caps 506, 508). The array 500 including the plurality of quartzresonator sensors 501 may be separated through a processes such as, forexample, a dicing process (e.g., a diamond-edged dicing saw), a scribingand breaking process, laser cutting, or any other suitable singulationor cutting process.

FIG. 11 is a cross-sectional side view of the array 500 of resonatorsensors 501 that have been separated to form individual resonatorsensors 501. The resonator sensors 501 may include any of the elements,features, and methods of forming discussed above with reference to FIGS.1 through 9.

Embodiments of the current disclosure may be particularly useful informing and providing resonator sensors (e.g., quartz resonator sensors)having a relatively simplified design such as a resonator sensor havingan active wafer including an inverted mesa design. Such resonatorsensors may enable the production thereof in quantities greater thanone. In other words, multiple sensors may be fabricated simultaneouslyout of sheets or plates of quartz and may be subsequently separated toform individual resonator sensors.

While the disclosure may be susceptible to various modifications andalternative forms, specific embodiments have been shown by way ofexample in the drawings and have been described in detail herein.However, it should be understood that the disclosure is not intended tobe limited to the particular forms disclosed. Rather, the disclosureencompasses all modifications, variations, combinations, andalternatives falling within the scope of the disclosure as defined bythe following appended claims and their legal equivalents.

1. An array of resonator sensors, comprising: an active wafer arraycomprising a plurality of unsingulated active wafers,; a firstunsingulated end cap array coupled to a first side of the active waferarray; and a second unsingulated end cap array coupled to a second sideof the active wafer array, wherein each unsingulated active wafercomprises a resonating portion, the resonating portion of eachunsingulated active wafer being out of contact with each of the firstand second unsingulated end cap arrays.
 2. The array of resonatorsensors of claim 1, wherein each resonator sensor of the array ofresonator sensors comprises a first cavity positioned proximate to acentral portion of an unsingulated active wafer on the first side of theactive wafer and a second cavity positioned proximate to the centralportion of the unsingulated active wafer on the second side of theactive wafer.
 3. The array of resonator sensors of claim 2, wherein thefirst cavity of each resonator sensor of the array of resonator sensorscomprises a first recess formed in a first face of the active wafer andthe second cavity of each resonator sensor of the array of resonatorsensors comprises a second recess formed in a second, opposing face ofthe active wafer.
 4. The array of resonator sensors of claim 2, whereinthe first cavity of each resonator sensor of the array of resonatorsensors comprises a first recess formed in a face of the active waferand the second cavity of each resonator sensors of the array ofresonator sensors comprises a second recess formed in a face of thesecond unsingulated end cap array.
 5. The array of resonator sensors ofclaim 2, wherein the first cavity of each resonator sensor of the arrayof resonator sensors comprises a first recess formed in a face of thefirst unsingulated end cap array and wherein the second cavity of eachresonator sensor of the plurality of resonator sensors comprises asecond recess formed in a face of the second unsingulated end cap array.6. The array of resonator sensors of claim 2, wherein the first cavityof each resonator sensor of the array of resonator sensors comprises afirst recess formed in a first face of the active wafer and a secondrecess formed in a face of the first unsingulated end cap array, andwherein the second cavity of each resonator sensor of the array ofresonator sensors comprises a third recess formed in a second, opposingface of the active wafer and a fourth recess formed in a face of thesecond unsingulated end cap array.
 7. The array of resonator sensors ofclaim 1, wherein each active wafer of the plurality of unsingulatedactive wafers comprises a central portion having a thickness less than athickness of an outer portion of the unsingulated active wafer.
 8. Thearray of resonator sensors of claim 1, wherein each of the unsingulatedactive wafer array, the first end cap array, and the second end caparray comprises a quartz plate.
 9. A plurality of thickness shear moderesonator sensors produced by a process, comprising: forming a pluralityof active wafer locations in a first sheet of material comprising:locating a central portion of each active wafer of the plurality ofactive wafer locations; and bounding the plurality of active waferlocations about the central portions thereof to form a first cavity on afirst side of each central portion and a second cavity on a second sideof each central portion to form an array of resonator sensors; andseparating the array of resonator sensors.
 10. The plurality ofthickness shear mode resonator sensors of claim 9, wherein forming aplurality of active wafer locations in a first sheet of material furthercomprises forming the central portion in each active wafer location ofthe plurality of active wafer locations to have a thickness less than athickness of an outer portion of the active wafer location.
 11. Theplurality of thickness shear mode resonator sensors of claim 9, whereinbounding the plurality of active wafer locations about the centralportions thereof and over the first and second cavities on the firstside and on the second side comprises: coupling a first side of thefirst sheet of material to a second sheet of material comprising aplurality of first end caps to cover the first side of the plurality ofactive wafer locations; and coupling a second side of the first sheet ofmaterial to a third sheet of material comprising a plurality of secondend caps to cover the second side of the plurality of active waferlocations.
 12. The plurality of thickness shear mode resonator sensorsof claim 11, wherein coupling a first side of the first sheet ofmaterial to a second sheet of material and coupling a second side of thefirst sheet of material to a third sheet of material comprises couplingwith a fused glass frit.
 13. The plurality of thickness shear moderesonator sensors of claim 9, further comprising forming the pluralityof resonator sensors to each exhibit a substantially quadrilateral crosssection.
 14. The plurality of thickness shear mode resonator sensors ofclaim 9, further comprising forming the plurality of resonator sensorsto each exhibit a substantially cylindrical cross section.
 15. A methodof forming a plurality of resonator sensors, comprising: forming aplurality of active wafer locations in a unitary structure; coupling aplurality of first end cap structures to a first side of the unitarystructure; coupling a plurality of second end cap structures to asecond, opposing side of the unitary structure; and separating theplurality of active wafer locations laterally between the end capstructures to form a plurality of discrete resonator sensors.
 16. Amethod of forming a plurality of resonator sensors, comprising: forminga plurality of active wafer locations in a first sheet of materialcomprising: locating a central portion of each active wafer of theplurality of active wafer locations; bounding the plurality of activewafer locations about the central portions thereof to form a firstcavity on a first side of each central portion and a second cavity on asecond side of each central portion to form an array of resonatorsensors; and separating the array of resonator sensors to form aplurality of discrete resonator sensors.
 17. The method of claim 16,wherein forming a plurality of active wafer locations in a first sheetof material further comprises forming the central portion in each activewafer location of the plurality of active wafer locations to have athickness less than a thickness of an outer portion of the active waferlocation.
 18. The method of claim 16, wherein bounding the plurality ofactive wafer locations about the central portions thereof and over thefirst and second cavities on the first side and on the second sidecomprises: coupling a first side of the first sheet of material to asecond sheet of material comprising a plurality of first end caps tocover the first side of the plurality of active wafer locations; andcoupling a second side of the first sheet of material to a third sheetof material comprising a plurality of second end caps to cover thesecond side of the plurality of active wafer locations and to form anarray of resonator sensors.
 19. The method of claim 16, whereinseparating the array of resonator sensors comprises separating the arrayof resonator sensors along a plane transverse to an interface betweenthe first sheet of material and at least one of the second sheet ofmaterial and the third sheet material.
 20. The method of claim 16,wherein forming a plurality of active wafer locations in a first sheetof material further comprises: forming a first electrode on the centralportion of each active wafer location of the plurality of active waferlocations on the first side of the first sheet of material; extendingthe first electrode to a conductive tab formed on an outer portion ofeach active wafer location of the plurality of active wafer locations onthe first side of the first sheet of material; forming a secondelectrode on the central portion of each active wafer location of theplurality of active wafer locations on the second side of the firstsheet of material; and extending the second electrode to a conductivetab formed on an outer portion of each active wafer location of theplurality of active wafer locations on the second side of the firstsheet of material.
 21. The method of claim 20, further comprising:providing at least one recess in an interface between the first sheet ofmaterial and the second sheet of material to expose a conductive tabformed on at least one active wafer location of the plurality of activewafer locations; and providing at least one recess in an interfacebetween the first sheet of material and the third sheet of material toexpose another conductive tab formed on at least one active waferlocation of the plurality of active wafer locations.
 22. The method ofclaim 16, wherein forming a plurality of active wafer locations in afirst sheet of material further comprises forming the plurality ofactive wafer locations in a quartz plate.
 23. A thickness shear moderesonator sensor, comprising: an active wafer comprising a resonatingelement; a first end cap coupled to a first side of the active wafer, atleast one surface of the active wafer and at least one surface of thefirst end cap forming a first cavity between the resonating element ofthe active wafer and the first end cap; and a second end cap coupled toa second, opposing side of the active wafer, at least one surface of theactive wafer and at least one surface of the second end cap forming asecond cavity between the resonating element of the active wafer and thesecond end cap, wherein the active wafer exhibits a substantiallyquadrilateral cross section taken in a direction along an interface ofthe active wafer and at least one of the first end cap and the secondend cap.
 24. The thickness shear mode resonator sensor of claim 23,wherein the active wafer further comprises: a first electrode disposedon the first side of the active wafer proximate a central portion of theactive wafer and extending to a first conductive tab extending along afirst outer portion of active wafer on the first side of the activewafer; and a second electrode disposed on the second side of the activewafer proximate the central portion and extending to a second conductivetab extending along a second outer portion of the active wafer on thesecond side of the active wafer.
 25. The thickness shear mode resonatorsensor of claim 24, wherein the first conductive tab extends along anentirety of a first edge on the first side of the active wafer, andwherein the second conductive tab extends along an entirety of a secondedge opposing the first edge on the second side of the active wafer. 26.The thickness shear mode resonator sensor of claim 23, wherein the firstend cap and the second end cap each exhibit a substantiallyquadrilateral cross section taken in the direction along the interfaceof the active wafer and at least one of the first end cap and the secondend cap.